Electronic device with backlit display

BACKGROUND

p-0002This relates generally to electronic devices and, more particularly, to electronic devices with displays and associated backlight structures.

p-0003Electronic devices such as computers and cellular telephones may have displays. Some displays such as plasma displays and light-emitting diode displays have arrays of display pixels that generate light. In displays of this type, backlighting is not necessary, because the display pixels themselves are illuminated. Other displays, such as liquid crystal displays, contain passive display pixels. The pixels in a liquid crystal display can alter the amount of light that is transmitted through the display to display information for a user, but do not produce light. As a result, it is often desirable to provide backlight for a liquid crystal display.

p-0004In a typical backlight structure for a display such as a liquid crystal display, a light guide plate is used to distribute backlight generated by a light source such as a light-emitting diode light source. Optical films such as a diffuser layer and brightness enhancing film may be placed on top of the light guide plate. A reflector may be formed under the light guide plate to improve backlight efficiency.

p-0005Conventional backlight arrangements are often not as compact as desired. The inclusion of optical films, provisions for registering the positions of the optical films within a device, the size and shape of the conventional light guide plates and light source, and other conventional backlight design features raise challenges when attempting to make backlights less bulky and more efficient.

p-0006It would therefore be desirable to be able to provide electronic devices with improved displays and backlights.

SUMMARY

p-0007An electronic device may have a display such as a liquid crystal display with backlight structures. The backlight structures may produce backlight that passes through layers in the display.

p-0008The display may include color filter elements and a thin-film transistor layer. The color filter elements may be interposed between the thin-film transistor layer and the backlight structures or the thin-film transistor layer may be interposed between the color filter elements and the backlight structures.

p-0009The backlight structures may be formed from optical fiber that is illuminated by a light source such as a light-emitting diode. The surface of the optical fiber may be provided with light leakage promotion features such as a surface texture that facilitates light leakage from within the optical fiber.

p-0010If desired, the backlight structures may be formed from a two-dimensional light source such as a two-dimensional array of light-emitting diodes. The two-dimensional array of light-emitting diodes may be formed from vertically mounted light-emitting diodes on a substrate or may be formed from a layer of organic light-emitting diodes.

p-0011Backlight structures may be provided with a light guide plate that includes a rectangular recess for receiving optical films. Backlight may be generated by launching light from a light source into the light guide plate.

p-0012The light guide plate may include bubbles or other internal light scattering structures to help diffuse the backlight.

p-0013A light guide plate in a backlight may be provided with alignment features that mate with alignment features on optical films.

p-0014Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0015<figref idrefs="DRAWINGS">FIG. 1</figref> is a diagram of an illustrative electronic device with a display such as a portable computer in accordance with an embodiment of the present invention.

p-0016<figref idrefs="DRAWINGS">FIG. 2</figref> is a diagram of an illustrative electronic device with a display such as a cellular telephone or other handheld device in accordance with an embodiment of the present invention.

p-0017<figref idrefs="DRAWINGS">FIG. 3</figref> is a diagram of an illustrative electronic device with a display such as a tablet computer in accordance with an embodiment of the present invention.

p-0018<figref idrefs="DRAWINGS">FIG. 4</figref> is a diagram of an illustrative electronic device with a display such as a computer monitor with a built-in computer in accordance with an embodiment of the present invention.

p-0019<figref idrefs="DRAWINGS">FIG. 5</figref> is a circuit diagram showing circuitry that may be used in an array of display pixels in accordance with an embodiment of the present invention.

p-0020<figref idrefs="DRAWINGS">FIG. 6</figref> is a circuit diagram of an illustrative display pixel in accordance with an embodiment of the present invention.

p-0021<figref idrefs="DRAWINGS">FIG. 7</figref> is a diagram of a portion of an illustrative array of color filter elements of the type that may be used for providing a display with the ability to display color images in accordance with an embodiment of the present invention.

p-0022<figref idrefs="DRAWINGS">FIG. 8</figref> is a cross-sectional view of an illustrative liquid crystal display having liquid crystal material interposed between an outer color filter array layer and an inner thin-film transistor layer in accordance with an embodiment of the present invention.

p-0023<figref idrefs="DRAWINGS">FIG. 9</figref> is a cross-sectional view of an illustrative liquid crystal display having an outer display layer that includes thin-film transistors and color filter elements in accordance with an embodiment of the present invention.

p-0024<figref idrefs="DRAWINGS">FIG. 10</figref> is a cross-sectional view of an illustrative liquid crystal display having a liquid crystal layer interposed between an outer thin-film transistor layer and an inner color filter layer in accordance with an embodiment of the present invention.

p-0025<figref idrefs="DRAWINGS">FIG. 11</figref> is a diagram of illustrative backlight structures that include an array of optical waveguides such as optical fiber waveguides in accordance with an embodiment of the present invention.

p-0026<figref idrefs="DRAWINGS">FIG. 12</figref> is a cross-sectional side view of illustrative backlight structures that include an optical fiber in accordance with an embodiment of the present invention.

p-0027<figref idrefs="DRAWINGS">FIG. 13</figref> is a cross-sectional end view of illustrative backlight structures that include optical fibers in accordance with an embodiment of the present invention.

p-0028<figref idrefs="DRAWINGS">FIG. 14</figref> is a diagram of illustrative backlight structures that include a structure for dispersing light that is interposed between an array of light-emitting diodes and an array of optical fibers in accordance with an embodiment of the present invention.

p-0029<figref idrefs="DRAWINGS">FIG. 15</figref> is a diagram of an illustrative light source coupled to backlight structures formed from an optical fiber using a tapered waveguide structure in accordance with an embodiment of the present invention.

p-0030<figref idrefs="DRAWINGS">FIG. 16</figref> is a diagram of illustrative backlight structures formed from an optical fiber that has been configured to follow a meandering path across the rear of a display accordance with an embodiment of the present invention.

p-0031<figref idrefs="DRAWINGS">FIG. 17</figref> is a diagram of an illustrative light-emitting diode array of the type that may be used in forming backlight structures for a display in accordance with an embodiment of the present invention.

p-0032<figref idrefs="DRAWINGS">FIG. 18</figref> is a cross-sectional side view of an illustrative light-emitting diode array of the type that may be used in forming backlight structures for a display in accordance with an embodiment of the present invention.

p-0033<figref idrefs="DRAWINGS">FIG. 19</figref> is a cross-sectional side view of a display having an opaque masking layer on the underside of a layer of polarizing material in accordance with an embodiment of the present invention.

p-0034<figref idrefs="DRAWINGS">FIG. 20</figref> is a cross-sectional side view of an illustrative display having a backlight light guide structure with a recessed portion for receiving optical films in accordance with an embodiment of the present invention.

p-0035<figref idrefs="DRAWINGS">FIG. 21</figref> is a diagram of a portion of a conventional display in a housing with registration pins that mate with holes in backlight optical films.

p-0036<figref idrefs="DRAWINGS">FIG. 22</figref> is a diagram of a display having backlight structures with alignment features such as holes that mate with corresponding alignment features such as protrusions on a backlight light guide structure in accordance with an embodiment of the present invention.

p-0037<figref idrefs="DRAWINGS">FIG. 23</figref> is a cross-sectional side view of an illustrative display in which optical films have been aligned with a light guide structure using protrusions on the light guide structure in accordance with an embodiment of the present invention.

p-0038<figref idrefs="DRAWINGS">FIG. 24</figref> is a cross-sectional side view of a conventional backlight for a display.

p-0039<figref idrefs="DRAWINGS">FIG. 25</figref> is a cross-sectional side view of a display backlight light guide structure having embedded scattering structures in accordance with an embodiment of the present invention.

p-0040<figref idrefs="DRAWINGS">FIG. 26</figref> is a cross-sectional side view of a display backlight light guide structure having multiple layers of embedded light scattering structures in accordance with an embodiment of the present invention.

p-0041<figref idrefs="DRAWINGS">FIG. 27</figref> is a cross-sectional side view of a display backlight light guide structure having embedded scattering structures distributed unevenly throughout the light guide structure in accordance with an embodiment of the present invention.

p-0042<figref idrefs="DRAWINGS">FIG. 28</figref> is a cross-sectional side view of a display backlight light guide structure having a textured surface light-leakage promotion structure in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

p-0043A display may be provided with backlight structures. The backlight structures may produce backlight for the display that helps a user of a device view images on the display in a variety of ambient lighting conditions. Displays with backlights may be provided in any suitable type of electronic equipment.

p-0044An illustrative electronic device of the type that may be provided with a backlit display is shown in <figref idrefs="DRAWINGS">FIG. 1</figref>. Electronic device <b>10</b> may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment.

p-0045As shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, device <b>10</b> may include a backlit display such as display <b>14</b>. Display <b>14</b> may be a touch screen that incorporates capacitive touch electrodes or other touch sensor components or may be a display that is not touch sensitive. Display <b>14</b> may include image pixels formed from liquid crystal display (LCD) components or other suitable display pixel structures. Arrangements in which display <b>14</b> is formed using liquid crystal display pixels are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display technology may be used in forming display <b>14</b> if desired.

p-0046Device <b>10</b> may have a housing such as housing <b>12</b>. Housing <b>12</b>, which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials.

p-0047Housing <b>12</b> may be formed using a unibody configuration in which some or all of housing <b>12</b> is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.).

p-0048As shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, housing <b>12</b> may have multiple parts. For example, housing <b>12</b> may have upper portion <b>12</b>A and lower portion <b>12</b>B. Upper portion <b>12</b>A may be coupled to lower portion <b>12</b>B using a hinge that allows portion <b>12</b>A to rotate about rotational axis <b>16</b> relative to portion <b>12</b>B. A keyboard such as keyboard <b>18</b> and a touch pad such as touch pad <b>20</b> may be mounted in housing portion <b>12</b>B.

p-0049In the example of <figref idrefs="DRAWINGS">FIG. 2</figref>, device <b>10</b> has been implemented using a housing that is sufficiently small to fit within a user's hand (i.e., device <b>10</b> of <figref idrefs="DRAWINGS">FIG. 2</figref> may be a handheld electronic device such as a cellular telephone). As show in <figref idrefs="DRAWINGS">FIG. 2</figref>, device <b>10</b> may include a backlit display such as display <b>14</b> mounted on the front of housing <b>12</b>. Display <b>14</b> may be substantially filled with active display pixels or may have an inactive portion and an inactive portion. Display <b>14</b> may have openings (e.g., openings in the inactive or active portions of display <b>14</b>) such as an opening to accommodate button <b>22</b> and an opening to accommodate speaker port <b>24</b>.

p-0050<figref idrefs="DRAWINGS">FIG. 3</figref> is a perspective view of electronic device <b>10</b> in a configuration in which electronic device <b>10</b> has been implemented in the form of a tablet computer. As shown in <figref idrefs="DRAWINGS">FIG. 3</figref>, backlit display <b>14</b> may be mounted on the upper (front) surface of housing <b>12</b>. An opening may be formed in display <b>14</b> to accommodate button <b>22</b>.

p-0051<figref idrefs="DRAWINGS">FIG. 4</figref> is a perspective view of electronic device <b>10</b> in a configuration in which electronic device <b>10</b> has been implemented in the form of a computer integrated into a computer monitor. As shown in <figref idrefs="DRAWINGS">FIG. 4</figref>, backlit display <b>14</b> may be mounted on the front surface of housing <b>12</b>. Stand <b>26</b> may be used to support housing <b>12</b>.

p-0052Display <b>14</b> may include an array of display pixels. Each display pixel may be used to control the light intensity associated with a portion of the display. An illustrative array of display pixels is shown in <figref idrefs="DRAWINGS">FIG. 5</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, display <b>14</b> may have a pixel array with rows and columns of pixels <b>40</b>. There may be tens, hundreds, or thousands of rows and columns of display pixels <b>40</b>. Display driver circuitry such as a display driver integrated circuit and, if desired, associated thin-film transistor circuitry formed on a display substrate layer may be used to produce data signals D on data lines in display <b>14</b> and may produce gate line signals G on gate lines in display <b>14</b>. During operation, the display driver circuitry may control the values of D and G to control the light intensity associated with each of the display pixels and thereby display images on display <b>14</b>.

p-0053<figref idrefs="DRAWINGS">FIG. 6</figref> is a circuit diagram of an illustrative display pixel in the pixel array of display <b>14</b>. Pixels such as pixel <b>40</b> of <figref idrefs="DRAWINGS">FIG. 6</figref> may be located at the intersection of each gate line and data line in display <b>14</b>.

p-0054A data signal D may be supplied to terminal <b>50</b> from one of the data lines in display <b>14</b>. Thin-film transistor <b>52</b> (e.g., a thin-film polysilicon transistor or an amorphous silicon transistor) may have a gate terminal such as gate <b>54</b> that receives gate line signal G from display driver circuitry (e.g., gate driver circuitry). When signal G is asserted, transistor <b>52</b> will be turned on and signal D will be passed to node <b>56</b> as voltage Vp. Data for display <b>14</b> may be displayed in frames. Following assertion of signal G in one frame, signal G may be deasserted. Signal G may then be asserted to turn on transistor <b>52</b> and capture a new value of Vp in a subsequent display frame.

p-0055Pixel <b>40</b> may have a signal storage element such as capacitor Cst or other charge storage element. Storage capacitor Cst may be used to store signal Vp between frames (i.e., in the period of time between the assertion of successive signals G).

p-0056Display <b>14</b> may have a common electrode coupled to node <b>58</b>. The common electrode (which is sometimes referred to as the Vcom electrode) may be used to distribute a common electrode voltage such as common electrode voltage Vcom to nodes such as node <b>58</b> in each pixel <b>40</b> of array <b>24</b>. Capacitor Cst may be coupled between nodes <b>56</b> and <b>58</b>. A parallel capacitance Clc arises across nodes <b>56</b> and <b>58</b> due to electrode structures in pixel <b>40</b> that are used in controlling the electric field through the liquid crystal material of the pixel (liquid crystal material <b>60</b>). As shown in <figref idrefs="DRAWINGS">FIG. 6</figref>, electrode structures <b>62</b> may be coupled to node <b>56</b>. Capacitance Clc is associated with the capacitance between electrode structures <b>62</b> and common electrode Vcom at node <b>58</b>. During operation, electrode structures <b>62</b> may be used to apply a controlled electric field (i.e., a field having a magnitude proportional to Vp-Vcom) across a pixel-sized portion of liquid crystal material <b>60</b> in pixel <b>40</b>. Due to the presence of storage capacitor Cst, the value of Vp (and therefore the associated electric field across liquid crystal material <b>60</b>) may be maintained across nodes <b>56</b> and <b>58</b> for the duration of the frame. Electrode structures <b>62</b> may have any suitable shape. For example, each display pixel may have an electrode that is formed from multiple electrode fingers.

p-0057The electric field that is produced across liquid crystal material <b>60</b> causes a change in the orientations of the liquid crystals in liquid crystal material <b>60</b>. This changes the polarization of light passing through liquid crystal material <b>60</b>. The change in polarization may be used in controlling the amount of light that is transmitted through each pixel <b>40</b> in display <b>14</b>.

p-0058To provide display <b>14</b> with the ability to display color images, display <b>14</b> may be provided with color filter elements. For example, display <b>14</b> may be provided with color filter elements such as red, green, and blue elements. Each color filter element may be used to impart color to the light associated with a respective display pixel in display <b>14</b>.

p-0059As shown in <figref idrefs="DRAWINGS">FIG. 7</figref>, color filter elements <b>80</b> may be formed in an array (e.g., an array of alternating red, green, and blue color filter elements) and may therefore sometimes be referred to as a color filter array <b>80</b> or color filter array structures <b>80</b>. The illustrative color filter array of <figref idrefs="DRAWINGS">FIG. 7</figref> shows how color filter elements may be arranged in rows and columns (e.g., rows and columns corresponding to respective rows and columns of display pixels <b>40</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>).

p-0060The color filter array for display <b>14</b> may be formed using structures that are located above or that are located below thin-film transistor structures in display <b>14</b>. An illustrative configuration for display <b>14</b> in which liquid crystal layer <b>60</b> is interposed between an upper (outer) color filter layer and a lower (inner) thin-film transistor layer is shown in <figref idrefs="DRAWINGS">FIG. 8</figref>.

p-0061With an arrangement of the type shown in <figref idrefs="DRAWINGS">FIG. 8</figref>, display <b>14</b> may receive backlight <b>82</b> from backlight structures <b>84</b>. Backlight structures <b>84</b> (which may sometimes be referred to as a backlight or backlight unit) may be located on the inner (lower) surface of display <b>14</b>. Backlight <b>82</b> from backlight structures <b>84</b> passes through layers <b>81</b> of display <b>14</b> and exits upper (outer) display surface <b>90</b>. A user of electronic device <b>10</b> such as viewer <b>86</b> may observe images on display <b>14</b> by looking in direction <b>88</b>.

p-0062Display layers <b>81</b> may include an upper polarizer layer such as layer <b>68</b> and a lower polarizer layer such as layer <b>74</b>. In a configuration of the type shown in <figref idrefs="DRAWINGS">FIG. 8</figref>, upper polarizer layer <b>68</b> may be attached to color filter array layer <b>70</b>. Color filter array layer <b>80</b> may be formed from a sheet of glass or plastic or other material that includes an array of color filter elements. Display <b>14</b> may be covered with a layer of glass or plastic (i.e., a display cover layer) or a layer such as color filter layer <b>80</b> may be provided with sufficient thickness (and therefore strength) to serve as the outermost structural layer of display <b>14</b>.

p-0063Lower polarizer layer <b>74</b> may be located between backlight <b>84</b> and thin-film transistor layer <b>92</b>. Thin-film transistor layer <b>92</b> may include a substrate such as substrate <b>94</b>. Substrate <b>94</b> may be formed from a layer of transparent material such as a sheet of clear glass or plastic. Thin-film transistor structures <b>96</b> may be formed on the surface of substrate <b>94</b> facing liquid crystal layer <b>60</b>. Thin-film transistor structures <b>96</b> may include thin-film circuitry such as thin-film transistors in gate driver circuitry and thin-film display pixel transistors such as transistor <b>52</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>, electrode structures such as electrode <b>62</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>, gate line conductors, data line conductors, and other thin-film circuitry for controlling display pixels <b>40</b>.

p-0064Display layers <b>81</b> may, if desired, include additional layers of material such as patterned opaque masking layers, smudge-resistance layers, anti-scratch layers, antireflection coatings, etc.

p-0065Liquid crystal layer <b>60</b> may be interposed between color filter layer <b>80</b> and thin-film transistor layer <b>92</b>. Sealant <b>99</b> (e.g., epoxy) may be provided around the periphery of display <b>14</b> to help contain liquid crystal layer <b>60</b>. As backlight <b>82</b> from backlight structures <b>84</b> passes through lower polarizer <b>74</b>, lower polarizer <b>74</b> polarizes light <b>82</b>. As polarized light <b>82</b> passes through liquid crystal material <b>60</b>, liquid crystal material <b>60</b> may rotate the polarization of light <b>82</b> by an amount that is proportional to the electric field through liquid crystal material <b>60</b>. If the polarization of light <b>82</b> is aligned in parallel with the polarization of polarizer <b>68</b>, the transmission of light <b>82</b> through layer <b>68</b> will be maximized. If the polarization of light <b>82</b> is aligned so as to run perpendicular to the polarization of polarizer <b>68</b>, the transmission of light <b>82</b> through layer <b>68</b> will be minimized (i.e., light <b>82</b> will be blocked). Display control circuitry may be used in adjusting the voltages Vp across the electrodes <b>62</b> of display pixels <b>40</b> in display <b>14</b>, thereby selectively lightening and darkening pixels <b>40</b> and presenting an image to a user of device <b>10</b> such as viewer <b>86</b>, viewing display <b>14</b> in direction <b>88</b>.

p-0066Displays such as display <b>14</b> may be mounted on one or more surfaces of device <b>10</b>. For example, displays such as display <b>14</b> may be mounted on a front face of housing <b>12</b>, on a rear face of housing <b>12</b>, or on other portions of device <b>10</b>.

p-0067If desired, the color filter array in display <b>14</b> may be located between the thin-film transistor layer and backlight structures <b>84</b>. Displays with layers that are stacked in this way may sometimes be referred to as having an inverted or flipped configuration, because the thin-film transistor layer is located above the color filter layer.

p-0068With one suitable inverted display arrangement, which is shown in <figref idrefs="DRAWINGS">FIG. 9</figref>, color filter elements <b>80</b> may be formed in a layer on the same substrate (substrate <b>94</b>) as thin-film transistor structures <b>96</b>. Substrate <b>94</b> may be formed from a clear sheet of plastic or glass or other suitable transparent substrate materials. Thin-film transistor structures <b>96</b> may be formed on the inner (lower) surface of substrate <b>94</b> (e.g., using semiconductor processing techniques such as photolithography). Color filter elements <b>80</b> (e.g., a color filter array layer) may be formed on the deposited layer of thin-film transistor structures (e.g., on the inner surface of substrate <b>96</b>). Color filter elements <b>80</b> include colored materials such as colored pigments or dyes and may be deposited using physical vapor deposition, chemical vapor deposition, ink-jet printing, spraying, pad printing, screen printing, spin-on coating, or other deposition techniques. The outer surface of the resulting thin-film transistor and color filter layer (i.e., display layer <b>100</b> of <figref idrefs="DRAWINGS">FIG. 9</figref>) may be covered with additional layers such as polarizer <b>68</b>.

p-0069Liquid crystal layer <b>60</b> may be interposed between layer <b>100</b> and lower polarizer <b>74</b>. Lower polarizer <b>74</b> may be formed from a polymer sheet. To provide a rigid support for lower polarizer layer <b>74</b>, lower polarizer layer <b>74</b> may, if desired, be mounted to a clear glass substrate and/or other support structures such as a supporting layer of material associated with backlight structures <b>84</b>.

p-0070Another suitable inverted display arrangement that may be used for display <b>14</b> is shown in <figref idrefs="DRAWINGS">FIG. 10</figref>. As in the configuration of <figref idrefs="DRAWINGS">FIG. 9</figref>, the color filter elements of <figref idrefs="DRAWINGS">FIG. 10</figref> are located between the thin-film transistor layer and the backlight. In the configuration of <figref idrefs="DRAWINGS">FIG. 10</figref>, however, color filter layer <b>80</b> of <figref idrefs="DRAWINGS">FIG. 10</figref> has been implemented using a substrate layer (e.g., a glass or plastic layer or other substrate) that is separate from thin-film transistor substrate layer <b>96</b>. In this configuration, liquid crystal material <b>60</b> may be interposed between thin-film transistor layer <b>92</b> (e.g., thin-film transistor substrate layer <b>94</b> and thin-film transistor structures <b>96</b>) and color filter array layer <b>80</b>. As with display <b>14</b> of <figref idrefs="DRAWINGS">FIG. 9</figref>, display <b>14</b> of <figref idrefs="DRAWINGS">FIG. 10</figref> may be provided with backlight <b>82</b> using backlight structures <b>84</b>.

p-0071In configurations of the types shown in <figref idrefs="DRAWINGS">FIGS. 9 and 10</figref>, the outermost substrate layer in display <b>14</b> may be formed from the thin-film transistor layer (i.e., thin-film transistor substrate <b>94</b>). Layer <b>94</b> may be implemented using a material that is thick enough (and therefore sufficiently strong) to allow layer <b>94</b> to be used in place of a separate cover glass layer. This may help reduce the size and weight of display <b>14</b>. If desired, a cover layer of glass or plastic may be used to cover the outer layer of display <b>14</b>.

p-0072As shown in <figref idrefs="DRAWINGS">FIGS. 8</figref>, <b>9</b>, and <b>10</b>, backlight <b>82</b> may travel vertically upwards (outwards) in through display layers <b>81</b> of display <b>14</b> to be viewed by a user such as viewer <b>86</b> looking at display <b>14</b> in direction <b>88</b>. Backlight <b>82</b> may be generated using any suitable type of backlight structure. For example, a clear sheet of glass or a clear sheet of plastic such as acrylic or other transparent member may be used to form a substantially planar light guide structure. This type of planar light guide structure may sometimes be referred to as a light guide plate.

p-0073A light-emitting diode array or other light source may be used to emit light into an edge of the light guide plate. The light guide plate in this type of backlight unit may guide light internally in accordance with the principle of total internal reflection. Light that leaks outwards from the light guide plate towards viewer <b>86</b> may serve as backlight <b>82</b>. A reflector in the backlight such as a sheet of white plastic or a layer of metal may be used to reflect light that leaks inwards from the light guide plate back in the outwards direction to serve as additional backlight <b>82</b>.

p-0074If desired, other types of backlight structures may be used in implementing backlight structures <b>84</b> for displays such as displays <b>14</b> of <figref idrefs="DRAWINGS">FIGS. 8</figref>, <b>9</b>, and <b>10</b>.

p-0075<figref idrefs="DRAWINGS">FIG. 11</figref> is a bottom view of illustrative backlight structures <b>84</b> showing how backlight structures <b>84</b> may be formed from optical waveguide structures such as optical fibers <b>154</b>. Optical fibers <b>154</b> may be formed from material such as plastic or glass (as examples). Fibers <b>154</b> may be formed from a single material (e.g., a single glass or plastic material) or may have an inner portion (e.g., a higher index of refraction portion) that is coated with an outer portion (e.g., a lower index of refraction portion).

p-0076Fibers <b>154</b> may have a circular cross-sectional shape (as an example). If desired, waveguide structures with other cross-sectional shapes may be used in forming backlight structures <b>84</b>. For example, optical waveguide structures for backlight structures <b>84</b> may have a square cross-sectional shape, a rectangular cross-sectional shape, an oval cross-sectional shape, a shape with curved edges, a shape with straight edges, a shape with a combination of curved and straight edges, or other suitable cross-sectional shapes. Optical fibers or other waveguides such as fibers <b>154</b> may be mounted to a support structure (e.g., a rigid or flexible glass or plastic substrate or a layer of resin) or may be mounted directly within housing structures <b>12</b> or other support structures.

p-0077Light sources such as one or more light-emitting diodes <b>150</b> may be used in providing backlight for display <b>14</b>. As shown in <figref idrefs="DRAWINGS">FIG. 11</figref>, for example, an array of light-emitting diodes <b>150</b> may be used to launch light into each of multiple optical fibers <b>154</b>.

p-0078Fibers <b>154</b> may be provided with light leakage promotion structures along their lengths to help scatter light out of fibers <b>154</b> through display <b>14</b>. As an example, the outermost (uppermost) surface of fibers <b>154</b> may be roughened. The roughened texture on fibers <b>154</b> may promote light leakage from fibers <b>154</b> through display layers <b>181</b>. If desired, a reflector may be provided under fibers <b>154</b> to help reflect stray light through display layers <b>81</b>.

p-0079As shown in <figref idrefs="DRAWINGS">FIG. 11</figref>, backlight structures <b>84</b> may be provided with one or more optical films <b>152</b>. Optical films <b>152</b> may be interposed between fibers <b>154</b> and display layers <b>81</b>. Examples of layers that may be included in optical films <b>81</b> include brightness enhancing film layers, diffusing film layers, and compensating film layers (as examples).

p-0080<figref idrefs="DRAWINGS">FIG. 12</figref> is a cross-sectional view of backlight structures such as backlight structures <b>84</b> of <figref idrefs="DRAWINGS">FIG. 11</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 12</figref>, light source <b>150</b> (e.g., a light-emitting diode) may emit light <b>158</b> into an adjacent end of optical fiber <b>154</b> (or other suitable optical waveguide structure). Optical fiber <b>154</b> may have light leakage promotion features such as features <b>154</b>F (e.g., surface roughness on the upper surface of fiber <b>154</b>). As light <b>158</b> propagates within fiber <b>154</b>, some of light <b>158</b> leaks out of fiber <b>154</b> upwards and forms backlight <b>82</b>A. Any light that escapes in the downwards direction (away from viewer <b>86</b>) may be reflected back in the upwards direction by reflector <b>156</b> (e.g., a sheet of white plastic, metal, or other reflective substance). Optical films <b>152</b> (e.g., a diffuser, a brightness enhancement film, etc.) may be interposed between optical fiber <b>154</b> and display layers <b>81</b> in display <b>14</b>.

p-0081<figref idrefs="DRAWINGS">FIG. 13</figref> is a cross-sectional end view of backlight structures <b>84</b> that have been formed from a series of optical fibers <b>154</b>. In the illustrative configuration of <figref idrefs="DRAWINGS">FIG. 13</figref>, each optical fiber <b>154</b> has been located immediately adjacent to another of optical fibers <b>154</b>. If desired, optical fibers <b>154</b> may be spread out so that fewer fibers are needed in backlight structures <b>84</b>. In configurations in which fibers <b>154</b> are spread out (and in configurations of the type shown in <figref idrefs="DRAWINGS">FIG. 13</figref>), diffuser layers may be used to ensure that backlight <b>82</b> is uniformly distributed over display <b>14</b>.

p-0082If desired, a diffusing and guiding structure such as optical diffusing and guiding structure <b>160</b> of <figref idrefs="DRAWINGS">FIG. 14</figref> may be used to diffuse and guide light <b>158</b> that has been emitted from light-emitting diodes <b>150</b>. Structure <b>160</b> may be formed from plastic, glass, or other transparent materials and may help distribute light <b>158</b> uniformly among multiple optical fibers <b>154</b> in backlight structures <b>84</b>. With this type of arrangement, fewer light-emitting diodes <b>150</b> may be used in providing illumination for fibers <b>154</b> (i.e., a larger number of fibers <b>154</b> may be used than light-emitting diodes <b>150</b>).

p-0083If desired, optical diffusing and guiding structures in backlight structures <b>84</b> such as structure <b>160</b> of <figref idrefs="DRAWINGS">FIG. 14</figref> or other structures may be provided with tapered portions to help concentrate light into fibers <b>154</b>. This type of arrangement is shown in <figref idrefs="DRAWINGS">FIG. 15</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 15</figref>, light-emitting diode <b>150</b> may emit light <b>158</b> into structure <b>160</b>′. Structures such as structure <b>160</b>′ of FIG. <b>15</b> may be provided between each of a plurality of light-emitting diodes and each respective one of a plurality of optical fibers <b>154</b>, if desired.

p-0084As shown in <figref idrefs="DRAWINGS">FIG. 16</figref>, optical fiber <b>154</b> may be configured to have a meandering path in backlight structures <b>84</b>. This type of arrangement may help distribute backlight over a relatively large area of display <b>14</b> without requiring the use of an overly large number of light-emitting diodes.

p-0085If desired, a two-dimensional array of light-emitting diodes may be used in providing display <b>14</b> with backlight. An illustrative two-dimensional light-emitting diode array is shown in <figref idrefs="DRAWINGS">FIG. 17</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 17</figref>, light-emitting diode array <b>162</b> may include signal lines such as control lines <b>164</b> that control an array of light-emitting diodes <b>166</b>. Light emitting diodes <b>166</b> may be organized in an array having multiple rows and multiple columns. There may be any suitable number or rows and columns of light-emitting diodes <b>166</b> in array <b>162</b> (e.g., ten or more rows and ten or more columns, 100 or more rows and 100 or more columns, 1000 or more rows and/or columns, etc.). Control lines <b>164</b> may run vertically and horizontally across array <b>162</b>. To conserve control circuit resources, it may be desirable to electrically short some of lines <b>164</b> together (e.g., so that multiple columns and/or rows of light-emitting diodes <b>166</b> may be controlled together). If desired, all of light-emitting diodes <b>166</b> may be controlled together (e.g., by configuring control lines <b>164</b> to power all of light-emitting diodes <b>166</b> at the same time using a common direct current or alternating current power signal). Light-emitting diodes <b>166</b> or relatively small sections of light-emitting diodes <b>166</b> may also be individually controlled (e.g., in configurations in which it is desirable to implement a localized dimming scheme for increasing the contrast ratio for display <b>14</b>).

p-0086Light-emitting diodes <b>166</b> may be white-light diodes or other monochromatic diodes (as an example). Each light-emitting diode <b>166</b> may be implemented using a separate surface-mount technology (SMT) packaged light-emitting diode component (e.g., a component that has solderable leads) or may be implemented using thin-film structures. For example, array <b>162</b> may be implemented by mounting rows and columns of SMT light-emitting diodes to a substrate such as a rigid or flexible printed circuit board, a layer of glass, or other suitable substrate. Light-emitting diode array <b>162</b> may also be implemented by depositing and patterning thin-film (e.g., polysilicon and/or amorphous silicon) light-emitting diode structures on a glass substrate, a rigid or flexible polymer substrate, or other suitable substrate. Light-emitting diode array <b>162</b> may, if desired, be formed from rows and columns of organic light-emitting diodes. Each organic light-emitting diode may include an organic emissive layer. An array of organic light-emitting diodes may be formed on a polymer substrate such as a polyimide substrate or a substrate formed from glass or other materials. The substrate on which the organic light-emitting diodes are formed may be flexible or may be rigid. Multiple layers of material may also be used in forming a substrate for light-emitting diodes <b>166</b>, if desired.

p-0087<figref idrefs="DRAWINGS">FIG. 18</figref> is a side view of an illustrative array of light-emitting diodes <b>116</b>. As shown in <figref idrefs="DRAWINGS">FIG. 18</figref>, light-emitting diodes <b>166</b> may be formed on substrate <b>168</b>. Substrate <b>168</b> may be formed from a layer of polyimide or other polymer (plastic), from a layer of glass, from a layer of ceramic, from other suitable substrate materials, or from a combination of two or more of these materials. One or more layers of patterned interconnects may be formed in substrate <b>168</b>, as illustrated by conductive lines <b>164</b> of <figref idrefs="DRAWINGS">FIG. 18</figref>. Lines <b>164</b> may be used for controlling light-emitting diodes <b>166</b>, as described in connection with <figref idrefs="DRAWINGS">FIG. 17</figref>.

p-0088As shown in <figref idrefs="DRAWINGS">FIG. 18</figref>, light-emitting diodes <b>166</b> may be configured to emit backlight such as backlight <b>82</b>D that travels in off-axis directions (i.e., directions that are angled with respect to surface normal <b>170</b>, which is perpendicular to the surface of substrate <b>168</b> and display <b>14</b>). If desired, light-emitting diodes <b>166</b> may be vertically mounted light-emitting diodes that are configured to emit backlight such as backlight <b>82</b>U in a direction that is parallel to surface normal <b>170</b> (i.e., in a vertical direction that is parallel to an axis such as axis <b>170</b> that is perpendicular to the surface of substrate <b>168</b>). Vertically mounted light-emitting diodes or other light-emitting diodes <b>166</b> that are configured to emit backlight vertically may help enhance backlight brightness.

p-0089An array of light-emitting diodes <b>166</b> such as array <b>162</b> of <figref idrefs="DRAWINGS">FIGS. 17 and 18</figref> (e.g., an organic light-emitting diode array) may be used as to form backlight structures <b>84</b> in displays such as displays <b>14</b> of <figref idrefs="DRAWINGS">FIGS. 8</figref>, <b>9</b>, and <b>10</b> (as examples).

p-0090In a display configuration of the type shown in <figref idrefs="DRAWINGS">FIG. 8</figref>, light-emitting diode array <b>162</b> may be mounted under polarizer <b>74</b> to serve as backlight structures <b>84</b> of <figref idrefs="DRAWINGS">FIG. 8</figref>. Optical films (e.g., diffuser films, brightness enhancement films, etc.) may be interposed between light-emitting diode array <b>162</b> and polarizer <b>74</b> or may be omitted. Polarizer <b>74</b> and, if desired, light-emitting diode array <b>162</b> may be formed from flexible materials. Substrate <b>94</b> of thin-film transistor layer <b>92</b> may be used to provide structural support for light-emitting diode array <b>162</b>, if desired.

p-0091In a configuration of the type shown in <figref idrefs="DRAWINGS">FIG. 9</figref>, light-emitting diode array <b>162</b> may also be mounted under polarizer <b>74</b> to serve as backlight structures <b>84</b>. As in the arrangement of <figref idrefs="DRAWINGS">FIG. 8</figref>, optical films (e.g., diffuser films, brightness enhancement films, etc.) may be interposed between light-emitting diode array <b>162</b> and polarizer <b>74</b> of <figref idrefs="DRAWINGS">FIG. 9</figref> or may be omitted. Polarizer <b>74</b> may be formed from a flexible material (e.g., a sheet of polymer). Accordingly, it may be desirable to support polarizer <b>74</b> with a rigid structure. The rigid structure may be formed by a rigid planar member that is mounted under light-emitting diode array <b>162</b> and/or that forms part of light-emitting diode array <b>162</b>. For example, light-emitting diode array <b>162</b> for backlight structures <b>84</b> of <figref idrefs="DRAWINGS">FIG. 9</figref> may be formed from a layer of glass (i.e., a glass substrate) or a rigid layer of plastic or other materials (i.e., a rigid plastic substrate or a rigid substrate of other materials). A flexible light-emitting diode array may be used, if desired. The flexible light-emitting diode may be supported by an underlying rigid planar support structure (e.g., a rigid layer of glass, plastic, ceramic, or metal, part of housing <b>12</b>, or other suitable support structures).

p-0092In a configuration of the type shown in <figref idrefs="DRAWINGS">FIG. 9</figref>, color filter layer <b>80</b> may, if desired, be formed from a rigid layer of glass, plastic, or other material. In this type of arrangement, color filter layer <b>80</b> may be used to provide rigidity for polarizer layer <b>74</b> and a flexible organic light-emitting diode array or other light-emitting diode array <b>162</b>. If desired, light-emitting diode array <b>162</b> may be formed from a rigid material such as glass, plastic, or ceramic or may be formed from a flexible substrate that is attached to a planar rigid support structure formed from glass, plastic, ceramic, or other suitable support structure materials, a portion of housing <b>12</b>, etc.

p-0093<figref idrefs="DRAWINGS">FIG. 19</figref> is a cross-sectional side view of an illustrative arrangement that may be used for display <b>14</b> in which an opaque masking layer such as opaque masking layer <b>170</b> has been formed on the underside of the periphery of lower polarizer layer <b>74</b>. As shown in <figref idrefs="DRAWINGS">FIG. 19</figref>, display <b>14</b> may include liquid crystal layer <b>60</b>. Liquid crystal layer <b>60</b> may be sandwiched between thin-film transistor layer <b>92</b> and color filter layer <b>80</b>. Driver integrated circuit <b>176</b> may be mounted on a ledge portion of thin-film transistor layer <b>92</b>. A layer of plastic, black ink, or other opaque masking material <b>174</b> may be formed between color filter layer <b>80</b> and thin-film transistor layer <b>92</b> in peripheral border regions of display <b>14</b> (i.e., in an inactive border region that does not contain any active display pixels <b>40</b>). Color filter layer <b>80</b>, liquid crystal layer <b>60</b>, and thin-film transistor layer <b>92</b> may be interposed between upper polarizer <b>68</b> and lower polarizer <b>74</b>. Backlight structures <b>84</b> may include a light guide plate such as light guide plate <b>180</b> and a light-emitting diode array or other light source <b>178</b>. Light source <b>178</b> (e.g., a light-emitting diode light source) may emit light into light guide plate <b>180</b> to serve as backlight <b>82</b>. Reflector <b>182</b> in backlight structures <b>84</b> may serve to reflect light through display layers <b>81</b> to viewer <b>86</b>.

p-0094With this type of arrangement, the edges of light guide plate <b>180</b> such as illustrative right-hand edge in <figref idrefs="DRAWINGS">FIG. 19</figref> may be bright due to reflected light from light-source <b>178</b>. To prevent bright edges <b>172</b> from being visible from the exterior of device <b>10</b>, opaque masking layer <b>170</b> may be provided on the lower surface of polarizer <b>74</b> in a shape that overlaps edges <b>172</b>. Opaque masking layer <b>170</b> may be formed in a peripheral region (e.g., an inactive border region) surrounding the edges of display <b>14</b> (e.g., layer <b>170</b> may be patterned to cover a rectangular ring-shaped area on the lower surface of polarizer <b>74</b>). Opaque masking layer <b>170</b> and layer <b>174</b> may be formed from black ink, opaque plastic, or other opaque materials. Due to the presence of masking layer <b>170</b>, edge <b>172</b> may be located in a region of device <b>10</b> that is relatively far from the edge of layer <b>92</b> and the edge of polarizer layer <b>74</b>, thereby creating additional room within device <b>10</b> for mounting other components.

p-0095As shown in <figref idrefs="DRAWINGS">FIG. 20</figref>, light-guide structures <b>180</b> may be configured to form a recess such as rectangular pocket <b>184</b> under display layers <b>181</b>. Light guide structures <b>180</b> may be formed from a plastic such as acrylic, glass, or other transparent material. Recess <b>184</b> may have a depth that is sufficient to receive optical films <b>186</b>. Optical films <b>186</b> may have a rectangular outline. Recess <b>184</b> may have a rectangular outline that is sufficiently large to receive optical films <b>186</b>. Optical films <b>186</b> may include films such as a diffusing layer, a brightness enhancing film, and other optical material layers. Light guide structures <b>180</b> (sometimes referred to as a planar light guide member or light guide plate) may have protruding sidewalls such as sidewall portions <b>180</b>′ that protrude upwards around the four edges at the periphery of display <b>14</b> and thereby define four sides for recess <b>184</b>. If desired, recess <b>184</b> may be sufficiently large to accommodate some of display layers <b>181</b> such as polarizer layer <b>74</b>.

p-0096Light <b>158</b> may be emitted from light source <b>150</b> into an edge or other surface of backlight light guide structures <b>180</b>. Light <b>158</b> may leak upwards out of upper surface of structure <b>180</b> to serve as backlight <b>82</b>. Reflector <b>182</b> may help reflect light <b>158</b> that has leaked downwards back in an upwards direction to serve as additional backlight <b>82</b>. Light guide plate <b>180</b> may serve as the main or exclusive structural element in backlight structures <b>84</b>. For example, light guide plate <b>180</b> may provide support for optical films <b>186</b> and/or reflector <b>182</b>. Reflector <b>182</b> may, as an example, be formed from a layer of metal that is deposited as a coating on light guide plate <b>180</b> or may be formed from a material that is attached to light guide plate <b>180</b>.

p-0097Adhesive such as adhesive <b>188</b> (e.g., epoxy) may be used to attach light-guide structure <b>180</b> of backlight structures <b>84</b> to display layers <b>81</b> (e.g., by attaching light-guide structure sidewall portions <b>180</b>′ to the lower surface of thin-film transistor layer <b>92</b>). If desired, light guide structures with a rectangular-pocket-shaped recess such as recess <b>184</b> of <figref idrefs="DRAWINGS">FIG. 20</figref> may be used in backlight structures such as backlight structures <b>84</b> of <figref idrefs="DRAWINGS">FIGS. 9 and 10</figref> (e.g., to provide backlight to a inverted-type display in which the color filter layer is interposed between the thin-film transistor structures and the backlight).

p-0098Backlight light guide structures such as structures <b>180</b> of <figref idrefs="DRAWINGS">FIG. 20</figref> may be provided with alignment features to help laterally align optical films <b>186</b>. The alignment features may be implemented in the form of protrusions on structures <b>180</b> or other suitable alignment features that are configured to mate with mating alignment features on optical films <b>186</b>.

p-0099A conventional arrangement for aligning optical films in a computer with a backlit display is shown in <figref idrefs="DRAWINGS">FIG. 21</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 21</figref>, optical films <b>202</b> are provided with tabs <b>208</b> that are received within corresponding notches in aluminum computer housing <b>200</b>. Aluminum pins <b>206</b> are formed as part of aluminum computer housing <b>200</b> and are received within openings <b>204</b> in optical films <b>202</b>. Under the influence of gravity, optical films <b>202</b> are pulled downwards in direction <b>212</b> and are held in place by the interaction between pins <b>206</b> and holes <b>204</b>. Optical films <b>202</b> are formed from plastic, whereas housing <b>200</b> is formed from aluminum. There is therefore a non-negligible mismatch in the coefficients of thermal expansion between housing <b>200</b> and optical films <b>202</b>. As a result, the gaps that are formed between tabs <b>208</b> and notches <b>210</b> tend to be large to accommodate thermal expansion mismatch.

p-0100Light guide structures such as light guide plate <b>180</b> of <figref idrefs="DRAWINGS">FIG. 20</figref> may be formed from a material such as plastic and may therefore be characterized by a coefficient of thermal expansion that is comparable to that of plastic (polymer) optical films <b>186</b>. By providing alignment features on light guide plate <b>180</b> and using light guide plate <b>180</b> as a structural element into which optical films <b>186</b> are assembled to form backlight structures <b>84</b> as described in connection with <figref idrefs="DRAWINGS">FIG. 20</figref>, gap sizes can be reduced and alignment tolerances can be enhanced.

p-0101An illustrative arrangement that may be used for backlight structures <b>84</b> in a configuration in which alignment features for backlight structure optical films are formed on light guide plate <b>180</b> is shown in <figref idrefs="DRAWINGS">FIG. 22</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 22</figref>, backlight structures <b>84</b> may include a light guide plate or other light guide structures <b>180</b>. Light guide structures <b>180</b> may be formed from a rectangular plate without sidewalls (i.e., without a recessed portion) or may be formed from a rectangular plate with protruding sidewall portions such as sidewall portions <b>180</b>′ of <figref idrefs="DRAWINGS">FIG. 20</figref>.

p-0102Light guide structures <b>180</b> may be provided with alignment features that mate with corresponding alignment features on optical films <b>186</b>. For example, light guide structures <b>180</b> may be provided with protrusions <b>180</b>P. Protrusions <b>180</b>P may be formed from rectangular pins or other protruding structures. Optical films <b>186</b> may be provided with mating openings such as holes <b>220</b>. When display <b>14</b> is held in a particular orientation in a laptop computer or compute monitor or in other suitable device arrangements, optical films <b>186</b> will be pulled in direction <b>222</b> under the influence of gravity. As a result, the edges of holes <b>220</b> will bear against corresponding edges of protruding portions <b>180</b>P of light guide structures <b>180</b>, aligning optical films <b>186</b> within backlight structures <b>84</b>.

p-0103<figref idrefs="DRAWINGS">FIG. 23</figref> is a cross-sectional view of backlight structures such as backlight structures <b>84</b> of <figref idrefs="DRAWINGS">FIG. 22</figref> that have been mounted within electronic device housing <b>12</b>. In the illustrative configuration of <figref idrefs="DRAWINGS">FIG. 23</figref>, gravity is causing optical films <b>186</b> to move in direction <b>222</b>. This causes upper edge <b>240</b> of opening <b>220</b> in optical films <b>186</b> to register against the adjacent edge of protruding portion <b>180</b>P of light guide plate <b>180</b>.

p-0104A conventional light guide plate is shown in <figref idrefs="DRAWINGS">FIG. 24</figref>. Light <b>300</b> from a light-emitting diode array enters the edge of light guide plate <b>302</b>. Textured lower surface <b>304</b> helps scatter light <b>300</b> so that some of light <b>300</b> leaks vertically upward from light guide plate <b>302</b> and, after passing through optical films <b>310</b> such as diffuser and brightness enhancing films, serves as backlight <b>306</b>. Reflector <b>308</b> reflects light that has leaked downwards back upwards to serve as additional backlight <b>306</b>.

p-0105If desired, light scattering features may be implemented within light guide structures such as a glass or plastic light guide plate. If light is sufficiently well dispersed (diffused) by the light scattering structures within the light guide plate, diffuser layers and other optical films may be omitted from backlight structures <b>84</b>. This type of arrangement is shown in <figref idrefs="DRAWINGS">FIG. 25</figref>. As shown in <figref idrefs="DRAWINGS">FIG. 25</figref>, backlight structures <b>84</b> include a light guide structure such as light guide plate <b>180</b> that includes internal structures <b>320</b>. Internal structures <b>320</b> may be formed from bubbles filled with air, particles formed from materials with an index of refraction that is greater than or less than the index of refraction of light guide plate <b>180</b>, or particles or voids with other properties that scatter light <b>158</b> from a light source such as a light-emitting diode light source. The inclusion of bubbles, particles, or other structures within the interior of light guide plate <b>180</b> may reduce or eliminate the need for diffusing films (as an example). Reflector <b>182</b> may be used to improve backlight efficiency.

p-0106In the illustrative configuration of <figref idrefs="DRAWINGS">FIG. 26</figref>, light guide structures <b>84</b> have been formed from a multilayer light guide plate that includes lower light guide plate layer <b>180</b>B (having a first type of bubbles or other internal structures <b>320</b>) and an upper light guide plate layer <b>108</b>A (having a second type of bubbles or other internal structures <b>320</b>). There may be three or more layers in light guide plate <b>180</b> if desired. Each layer may have a different type of internal structures (e.g., a different density of internal structures, internal structures of different sizes, shapes, internal structures formed from different materials, etc.). Reflector <b>182</b> may be used to improve backlight efficiency.

p-0107In the illustrative configuration of <figref idrefs="DRAWINGS">FIG. 27</figref>, light guide plate <b>180</b> of backlight structures <b>84</b> has been provided with bubbles or other internal structures <b>320</b> with sizes, shapes, and/or materials properties that change smoothly (e.g., structure types that vary following a linear or curved gradient). As an example, the properties of internal structures <b>320</b> may vary as a function of vertical distance within light guide plate <b>180</b>. Backlight efficiency may be enhanced using reflector <b>182</b>, if desired.

p-0108Another illustrative arrangement for backlight structures <b>84</b> is shown in <figref idrefs="DRAWINGS">FIG. 28</figref>. In the configuration of <figref idrefs="DRAWINGS">FIG. 28</figref>, light guide plate <b>180</b> has been provided with a textured surface or other surface treatment on the upper surface of light guide plate <b>180</b> that promotes light leakage. The inclusion of textured surface <b>322</b> causes light <b>158</b> to exit light guide plate <b>180</b> to serve as backlight <b>82</b>. Reflector <b>182</b> may be used to enhance backlight efficiency for backlight structures <b>84</b>.

p-0109The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.